It is of critical importance that the entry of objects into a surgical field and into a surgical site, as well, as their removal be very carefully reconciled so as to avoid inadvertent retention of an object within a patient. Counting objects entering and exiting a surgical field is a conventional operating room procedure. Such practices greatly reduce the risk of an object being inadvertently retained within the patient. Such procedures typically involve the manual counting of objects entering and exiting the surgical field, as well as the visual examination of the surgical site. It is critical that such procedures be completed before the surgical site is closed. In the event that the surgical site needs to be closed with minimum delay, it is necessary to finish the verification that there is no object retained in the patient as quickly as possible. It is therefore desirable to provide effective and timely means and methods of monitoring objects entering and exiting a surgical field with a high degree of accuracy and with minimum effort from medical personnel.